The present invention relates to a hydraulically actuable dual fuel injection valve and a dual needle assembly, for injecting two different fuels into the combustion chamber of an internal combustion engine.
Because of its ready availability, low cost and potential for reducing particulate emissions, natural gas is a promising substitute for diesel fuel for fuelling compression ignition engines, commonly known as xe2x80x9cdiesel-cyclexe2x80x9d engines. Persons skilled in the technology involved here will understand that natural gas is just one example of a preferred fuel, and that other fuels are also suitable, such as hydrogen, propane and other fuels that are cleaner burning substitutes for diesel fuel. A cleaner burning substitute fuel for diesel is defined as a fuel that can be used in an engine to substantially match the performance of a diesel-fuelled engine with lower particulate matter and/or nitrogen oxide (NOx) emissions.
Conventional methods of introducing a gaseous fuel into an engine premix all of the gaseous fuel with the intake air, which is a method known as xe2x80x9cfumigationxe2x80x9d. Engines using such an approach have been unable to match the power, performance, and efficiency of diesel-fuelled engines. The applicant has found that the inherent favorable operating characteristics and high efficiency of conventional diesel-fuelled engines can be preserved when at least some of the gaseous fuel is introduced directly into the engine""s combustion chamber, late in the compression stroke.
A problem with gaseous fuels such as natural gas is that, compared to diesel fuel, much higher temperatures and pressures are typically needed to auto-ignite the fuel. A solution to this problem, which allows the preservation of the major components of diesel-cycle engines is to inject a small amount of more auto-ignitable fuel such as diesel fuel, to initiate the ignition and combustion of the cleaner burning gaseous fuel.
Using a pilot fuel in addition to a main charge of gaseous fuel requires the installation of at least two independently operable injection valves, one for the pilot fuel and one for the gaseous main fuel. To avoid having to redesign and replace the cylinder head, it is preferable to employ a gaseous and liquid fuel injection valve that fits into the same opening as a conventional diesel fuel injection valve. Accordingly, there is a need for a gaseous and liquid fuel injection valve arrangement that allows independent introduction of liquid pilot fuel and gaseous main fuel directly into the combustion chamber, and that has the same exterior dimensions as a conventional diesel injection valve.
A dual fuel injection valve separately injects a main fuel and a pilot fuel into a combustion chamber of an internal combustion engine. The injection valve comprises:
(a) a hollow injection valve body comprising:
a hydraulic fluid inlet port through which pressurized hydraulic fluid can be introduced into fluid passages and a control chamber disposed within the interior of the valve body;
a hydraulic fluid drain port through which hydraulic fluid can be drained from the control chamber;
at least one control valve that is operable to selectively direct the flow of the hydraulic fluid and control hydraulic fluid pressure within the control chamber to influence movement of at least one of an outer needle and an inner needle between respective open and closed positions;
a first-fuel inlet port through which a first fuel can be introduced at injection pressure into the valve body;
a first-fuel passage provided within the valve body and extending between the first-fuel inlet port and a first-fuel cavity associated with the outer needle;
a second-fuel inlet port through which a second fuel can be introduced into the valve body;
a second-fuel passage connecting the second-fuel inlet port to a second-fuel cavity associated with the inner needle; and
(b) a dual needle assembly comprising:
the outer needle, which is hollow and disposed within the injection valve body, wherein the outer needle is movable between a closed position in which a first sealing surface associated with the outer needle contacts a first seat associated with the body and an open position in which the first sealing surface is spaced apart from the first seat, allowing the first fuel to flow from within the first-fuel cavity into the combustion chamber through at least one first-fuel ejection port; and
the inner needle, which is disposed within the hollow outer needle, wherein the inner needle is movable between a closed position in which a second sealing surface associated with the inner needle contacts a second seat associated with the outer needle and an open position in which the second sealing surface is spaced apart from the second seat, allowing the second fuel to flow from within the second-fuel cavity into the combustion chamber through at least one second-fuel ejection port.
In one embodiment, the first fuel is a main fuel and the second fuel is a pilot fuel that is more auto-ignitable than the main fuel. The hollow outer needle preferably serves as an inner valve body and the second-fuel cavity is preferably an annular cavity disposed between the inner needle and the outer needle.
The control chamber is preferably employed to influence the position of the outer needle and an inlet fluid passage connects the control chamber to the hydraulic fluid inlet port, a drain fluid passage connects the control chamber to the drain port, and the control valve is operable to selectively control the flow of hydraulic fluid between the control chamber and the drain port or the hydraulic fluid inlet port to modulate pressure within the control chamber between drain pressure, when pressure within the control chamber is associated with pressure at the drain port, and rail pressure, when pressure within the control chamber is associated with pressure at the hydraulic fluid inlet port.
The dual needle assembly is preferably dynamically disposed within the control chamber and the volume of the control chamber is preferably variable in response to movement of the dual needle assembly. Pressure within the control chamber is preferably held at rail pressure to generate a hydraulic force that contributes to maintaining the outer needle in the closed position. A spring preferably provides an additional closing force that cooperates with the hydraulic force to maintain the outer needle in the closed position. Fuel pressure within the first-fuel cavity preferably generates an opening force acting on the outer needle whereby the outer needle is movable to the open position under the influence of the opening force when pressure within the control chamber is reduced to close to drain pressure.
The outer needle is preferably biased in the closed position when pressure within the control chamber is at drain pressure or close to drain pressure (that is, the control chamber pressure has a value sufficiently near drain pressure such that the outer needle is nevertheless biased in the closed position) and the outer needle is movable to the open position when hydraulic fluid pressure within the control chamber is at rail pressure. Preferably, a spring biases the outer needle in the closed position. The outer needle preferably comprises a shoulder disposed within the first control chamber and when pressure within the first control chamber is raised to rail pressure the hydraulic force is applied to the shoulder.
In another embodiment of the present injection valve, the body preferably further comprises a second control chamber employed to influence the position of the inner needle and a second control valve is preferably operable to selectively control pressure of hydraulic fluid within the second control chamber to generate a hydraulic force that contributes to positioning the inner needle in one of the closed or open positions. The inner needle preferably comprises a shoulder that is dynamically disposed within the second-fuel cavity and the shoulder provides an area for receiving an opening force generated by fuel pressure within the second-fuel cavity. The injection valve preferably further comprises an inner spring disposed within the dual needle assembly that biases the inner needle in the closed position. The hydraulic force generated within the second control chamber preferably provides a force that acts on a movable intensifier piston that is operable to pressurize the second fuel. The second fuel can thereby be pressurized to an intensified pressure to generate an opening force acting on the inner needle that compresses the inner spring to move the inner needle to the open position.
The hydraulic fluid pressure within the second control chamber preferably generates a hydraulic force that acts directly upon the dual needle assembly to influence positioning of the inner needle in one of the closed or open positions. The rail pressure within the second control chamber is preferably employed to generate a hydraulic force that contributes to maintaining the inner needle in the closed position.
The second control chamber is preferably disposed within the dual needle assembly and a member associated with the inner needle is preferably dynamically disposed within the second control chamber such that the volume of the second control chamber is variable in response to movement of the member which causes a corresponding movement of the inner needle.
An inner spring preferably provides an additional closing force that cooperates with the hydraulic force to maintain the inner needle in the closed position.
The inner needle is preferably movable to the open position under the influence of an opening force generated by hydraulic fluid at rail pressure within the second control chamber. The inner needle is preferably biased in the closed position by an inner spring and the second control chamber is the second-fuel cavity. The inner needle is thereby movable to the open position when pressure within the second-fuel cavity is at rail pressure.
In another embodiment of the present injection valve, the dual needle assembly preferably further comprises a cap dynamically disposed within the control chamber between the outer needle and the valve body such that, when the control chamber associated with the outer needle is filled with hydraulic fluid at rail pressure, the hydraulic force urges the cap towards the outer needle and a closing force is transmitted through the cap to the outer needle. The outer needle is preferably movable to the open position under the influence of fuel pressure within the first-fuel cavity acting on the outer needle when pressure within the control chamber is reduced to drain pressure. The injection valve preferably further comprises an inner spring disposed within the hollow outer needle between the cap and the inner needle for biasing the inner needle in the closed position. The cap preferably comprises an open-ended bore facing the inner needle and the assembly preferably further comprises an inner spring disposed within the bore between the cap and the inner needle. The inner spring preferably biases the inner needle in the closed position. The cap is preferably detached from the outer needle such that the inner spring can expand to contribute to holding the outer needle in the closed position by spacing the cap from the outer needle. The cap is preferably joinable in fixed relationship to the outer needle. The cap is preferably releasably joined to the outer needle by a threaded connection or by interlocking features.
In another embodiment of the present injection valve, the dual needle assembly preferably further comprises an inner valve body comprising:
the outer needle;
a hollow inner valve housing joined to the outer needle; and
a cap joined to the hollow inner valve housing.
The inner needle is preferably disposed within the outer needle and the second-fuel cavity is an annular space between the inner needle and the outer needle. At least one of an inner spring and the second control chamber is preferably disposed within the hollow inner valve housing for biasing the inner needle in the closed position. The cap is preferably dynamically disposed within the control chamber associated with the outer needle. The present injection valve preferably further comprises an outer spring disposed between the cap and the valve body. The outer spring thereby contributes to biasing the outer needle in the closed position.
In another embodiment of the present injection valve, the dual needle assembly further comprises:
a cap dynamically disposed within the control chamber associated with the outer needle whereby a closing force can be transmitted through the cap to the outer needle; and
an inner spring disposed between the cap and a member associated with the inner needle.
The inner spring contributes to biasing the inner needle in the closed position by imparting a closing force through the member to the inner needle. The inner spring can also contribute to biasing the outer needle in the closed position by expanding to space the cap from the outer needle.
In another embodiment of the present injection valve, the outer needle preferably further comprises a shoulder disposed within the control chamber associated with the outer needle. The outer needle is thereby movable to the open position when the control chamber is filled with hydraulic fluid at rail pressure. The present injection valve preferably further comprises a spring disposed between the dual needle assembly and the injection valve body for biasing the outer needle in the closed position.
A dual needle assembly for a dual fuel injection valve independently and separately injects two different fuels into a combustion chamber. The dual needle assembly comprises:
a hollow outer needle that can be dynamically disposed within a hollow injection valve body, wherein the outer needle is movable within the injection valve body between a closed position when a first sealing surface associated with the outer needle is urged against a first seat associated with the injection valve body, and an open position when the first sealing surface is spaced apart from the first seat;
an inner valve body comprising:
the outer needle; and
a cap joined to the outer needle;
an inner needle dynamically disposed within the outer needle, wherein the inner needle is movable within the outer needle between a closed position when a second sealing surface associated with the inner needle is urged against a second seat associated with the outer needle, and an open position when the second sealing surface is spaced apart from the second seat;
an inner spring disposed within the inner valve body between the cap and the inner needle which contributes to biasing the inner needle in the closed position; and
at least one fuel ejection port provided in the outer needle that allows fuel to be ejected from an inner fuel cavity within the inner valve body when the inner needle is in the open position.
In one embodiment of the present dual needle assembly, the inner fuel cavity is preferably an annular volume disposed between the inner needle and the outer needle. The inner needle preferably has an outer diameter less than the inside diameter of the hollow outer needle. The inner valve body preferably further comprises a hollow inner valve housing disposed between and joined to the outer needle and the cap. The inner valve housing preferably comprises a bore for housing the inner spring and the space defined by the bore is sealed from the inner fuel cavity by a match fit between the inner needle and the outer needle. The space defined by the bore of the inner valve housing is preferably pressurizable with hydraulic fluid supplied from fluid passages within the injection valve body. Pieces of the inner valve body are preferably releasably joined together by interlocking features. The dual needle assembly interlocking features are preferably threaded joints. Pieces of the inner valve body are permanently joined together. The permanently joined pieces are preferably welded together. Other pieces of the inner valve body are preferably releasably joined together.
Another dual needle assembly for a dual fuel injection valve independently and separately injects two different fuels into a combustion chamber. The dual needle assembly comprises:
a hollow outer needle comprising an open end and an opposite sealing end, which comprises a first sealing surface, and the outer needle can be dynamically disposed within a hollow injection valve body, wherein the outer needle is movable within the injection valve body between a closed position when the first sealing surface is urged against a first seat associated with the injection valve body, and an open position when the first sealing surface is spaced apart from the first seat;
a cap associated with and detached from the open end of the outer needle, wherein the cap can be dynamically disposed within a control chamber of the injection valve body such that hydraulic fluid pressure within the control chamber can apply a force that is transmitted through the cap to the outer needle to influence the position of the cap and outer needle;
an inner needle dynamically disposed within the outer needle, the inner needle comprising a supported end opposite to a sealing end, which comprises a second sealing surface, wherein the inner needle is movable within the outer needle between a closed position when the second sealing surface is urged against a second seat associated with the outer needle, and an open position when the second sealing surface is spaced apart from the second seat;
an inner spring disposed within the inner valve body between the cap and the inner needle, whereby the inner spring contributes to biasing the inner needle in the closed position, and the inner spring can also contribute to biasing the outer needle in the closed position by expanding to space the cap away from the outer needle; and
at least one fuel ejection port that allows fuel to be ejected from an inner fuel cavity within the hollow outer needle when the inner needle is in the open position.
In one embodiment of the present dual needle assembly, the supported end of the inner needle preferably has an outside diameter that is match fit with an inside diameter of a bore provided in the outer needle. The present dual needle assembly preferably further comprises a member that supports one end of the inner spring and that transmits closing forces from the inner spring to the inner needle and to the outer needle. The spring is preferably a coil spring and the member preferably comprises a flange for receiving one end of the coil spring and a stem that extends through the coil spring. The stem thereby cooperates with the cap to limit travel of the inner needle.
A method of operating a dual fuel injection valve independently and separately injects two different fuels into a combustion chamber of an internal combustion engine. The method comprises:
(a) supplying a first fuel at injection pressure to a first-fuel cavity within the injection valve;
(b) selectively applying a first closing force to a first needle to prevent the first fuel from being injected into the combustion chamber by holding the first needle in a closed position against a first seat;
(c) selectively injecting the first fuel into the combustion chamber from the first-fuel cavity by at least one of applying to the first needle a first opening force greater than the first closing force and reducing the first closing force such that the first needle is spaced apart from the first seat;
(d) supplying a second fuel at less than injection pressure to a second-fuel cavity within the injection valve;
(e) selectively applying a second closing force to a second needle to prevent the second fuel from being injected into the combustion chamber by holding the second needle in a closed position against a second seat;
(f) selectively operating an intensifier located within the injection valve to intensify the pressure of the second fuel within the second-fuel cavity to generate a second opening force acting on the second needle that is greater than the second closing force, such that the second needle is spaced apart from the second seat and the second fuel is injected into the combustion chamber from the second-fuel cavity.
The present method preferably further comprises metering the second fuel by controlling the stroke of the intensifier. The pressure of the first fuel within the first-fuel cavity preferably contributes to the first opening force by applying an opening force to a shoulder of the first needle. The first closing force is preferably generated by directing a pressurized hydraulic fluid to a control chamber within the injection valve and the first fuel is preferably injected when pressure within the control chamber is reduced by draining hydraulic fluid from the control chamber. The present method preferably further comprises selectively operating an electronically controlled valve to control the flow of the hydraulic fluid to and from the control chamber.
In another embodiment of the present method the first closing force is preferably generated by a compressed spring and the first fuel is preferably injected into the combustion chamber by directing a pressurized hydraulic fluid to a control chamber within which a shoulder of the first needle is dynamically disposed. The hydraulic fluid pressure acting on the shoulder preferably contributes to the first opening force such that the first opening force is greater than the first closing force. The present method preferably further comprises selectively operating an electronically controlled valve to control the flow of the hydraulic fluid to and from the control chamber.
In another embodiment of the present method, the intensifier is preferably hydraulically actuated by selectively supplying or draining a pressurized hydraulic fluid from a piston chamber within which an intensifier piston is dynamically disposed. The present method preferably further comprises selectively operating an electronically controlled valve to control the flow of the hydraulic fluid to and from the piston chamber.
In another embodiment of the present method, a compressed spring preferably contributes to the second closing force. The present method preferably further comprises utilizing hydraulic fluid pressure in a second control chamber to contribute to the second closing force applied to the second needle.
Another method of operating a dual fuel injection valve independently and separately injects two different fuels into a combustion chamber of an internal combustion engine. The method comprises:
(a) supplying a first fuel at injection pressure to a first-fuel cavity within the injection valve;
(b) selectively applying a first closing force to a first needle to prevent the first fuel from being injected into the combustion chamber by holding the first needle in a closed position against a first seat;
(c) selectively injecting the first fuel into the combustion chamber from the first-fuel cavity by at least one of applying a first opening force to the first needle that is greater than the first closing force and reducing the first closing force such that the first needle is spaced apart from the first seat;
(d) supplying a second fuel at injection pressure to a second-fuel cavity within the injection valve;
(e) selectively applying a second closing force to a second needle to prevent the second fuel from being injected into the combustion chamber by holding the second needle in a closed position against a second seat;
(f) selectively injecting the second fuel into the combustion chamber from the second-fuel cavity by at least one of applying a second opening force to the second needle that is greater than the second closing force and reducing the second closing force such that the second needle is spaced apart from the second seat.